Polycarbodiimide treatments

ABSTRACT

Porous collagen fiber matrix including natural leather having improved dynamic water resistance and the process for making it comprising treating tanned anionically charged water wetted collagen fiber matrix with chromium complex and with carbodiimide.

United States Patent [1 1 Schuster et al.

[ 1 Nov. 25, 1975 1 POLYCARBODIIMIDE TREATMENTS [21] Appl. No.: 382,343

[52] U.S. Cl. 8/94.2l; 8/9422; 8/9427 [51] Int. Cl. Cl4C 3/06; C14C 9/02 [58] Field of Search 8/9421, 94.27

[56] References Cited UNITED STATES PATENTS 2,853,518 9/1958 Balon 260/551 3,450,562 6/1969 Hoeschele 117/155 3574517 7/1967 Elvrum 8/9416 3.574.518 4/1971 Dctomaso. 8/94 21 3.668,l24 6/1972 Cassella 252/8 57 Primary Examiner.loseph L. Schofer Assistant Examiner-A. L. Clingman Attorney, Agent, or Firm-Alexander, Sell. Steldt & DeLal-lunt [5 7] ABSTRACT Porous collagen fiber matrix including natural leather having improved dynamic water resistance and the process for making it comprising treating tanned anionically charged water wetted collagen fiber matrix with chromium complex and with carbodiimide.

8 Claims, No Drawings POLYCARBODIIMIDE TREATMENTS This invention relates to improved leathers and the process for preparation of such leathers. Further, this invention relates to a process for improving the dynamic water resistance of a porous collagen fiber matrix such as leather. Still further, the invention relates to porous collagen fiber matrices having both static and dynamic water resistance.

One of the characteristics of porous collagen fiber matrices which makes them eminently suitable for use in articles of clothing such as gloves, shoes or garments is the ability to transmit moisture vapor from the skin of the wearer to the outside, facilitating extended use without discomfort. Treatments to improve the protection of the wearer from the environmental hazards, particularly liquid water, should not damage this moisture vapor transmission characteristic of the collagen matrlx.

Leathers from animal hides can be divided into two broad categories. Because grain leathers retain the tightly knit external surface of natural hide, they provide the maximum protection, but tend to be somewhat stiff and conform with greater or less difficulty to motion of the wearer. Suede leathers, those in which the surface of the material is abraded to provide a napped surface, can be extremely flexible, but tend both to absorb and to transmit liquid water and, additionally, are especially subject to oily and water-bornlstains. The term collagen fiber matrix includes not only natural leathers but also certain synthetic leathers.

Treatment of the leather with Werner complexes, particularly of chromium and carboxylic acids and more recently of chromium complexes of fluoroaliphatic carboxylic acids, significantly improves the resistance of leathers to water and oil; however, continued flexing in the presence of liquid waterfacilitates penetration. It was found, as shown in US. Pat. No. 3,574,518, that a combination of chrome complex plus a urethane, where one or the other or both components could be fluorinated, provided not only resistance to static application of water, but provided very significantly improved resistance to passage through the material of liquid water under dynamic conditions. Oil repellency is attained only when one or the other component contains organically bound fluorine. In the absence of fluorinated material, neither static nor dynamic oil repellency is exhibited. A chrome complex in another combination was used in US. Pat. No. 3,668,124.

It is an object of this invention to provide a process for conferring static and dynamic water resistance on collagen fiber matrices. Another object of the invention is to provide collagen fiber matrices and particularly suede leathers having improved retention of static and dynamic water repellency after abrasion. Other objects will become apparent from the reading of this disclosure. I

In accordance with these and other objects of the invention, it has now been found that the application of the chromium complex of organic carboxylic lacidin conjunction with a carbodiimide composition provides an improved treatment for anionically charged collagen fiber matrices, particularly leathers which Show both desirable abrasion resistant static and dynamic properties and additionally, in some instances, oil repellency. When both carbodiimide and chromium compors are very irritating to the workers. The present pro- 2 plex are.fluorine free, the leather acquires satisfactory static and dynamic water resistance, but is neither oil resistant nor oil repellent. It is, therefore, generally desirablethat'one or the other or both components contain fluoroaliphatic radicals.

The term fluoroaliphatic radical willbe understood to refer to, a fluorinated, monovalent, non-aromatic, aliphatic radical of at least three carbon atoms the chain of which may be straight, branched, or, if suffi-- respects more reactive. Saturated fluoroaliphatic radi-,

cals are preferred. Fluoroaliphatic radicals of more than about 18 carbon atoms generally result in relatively less efficient use of fluorine.

When fluoroaliphatic carbodiimides are employed, it is generally found that a given level of static and dynamic resistance can be achieved at a markedly lower level of fluorine content than. is necessary when a fluoroaliphatic urethane is used, as in the prior art. Additionally, the resistance of the surface to loss of properties by abrasion, particularly in the case of the suede leathers, is greatly improved in the case of the carbodiimide-treated leathers. Yet another advantage of the present process is that the carbodiimide is preferably applied as an aqueous suspension or emulsion, whereas the preferred method of applying theurethane adduct I involves the introduction of the material to the tanning drum in the form of a solution in a water-miscible organic solvent, particularly tetrahydrofuran. This solvent is moderately toxic, highly flammable and its vacess thus avoids the hazard and annoyance of using tetrahydrofuran.

The present process is applicable to chrome-tanned leathers which have been further treated as by retanning, dyeing, etc., so as to convert the cationically charged blue, i.e., chrome-tanned, leather to an anionically charged leather which appears to facilitate the acceptance of the present treatment. Suitable materials for use as retanning, dyeing, etc. agents will be readily recognized by those skilled in the leather arts.

The weight ratio of chromium complex of carboxylic acid to carbodiimide composition used in the process of the invention varies broadly within the range of 0.1 to 10, and preferably 0.3 to 3. As noted above. it is preferred that one or the other or both include fluoroaliphatic groups incorporated in the combination in proportions such that at the pick-up level to be achieved there will be at least 0.25% and up to 3.0% by weight of carbon-bonded fluorine on the leather and preferably from 0.8% to 1.5%

Chrome-tanned fat-liquored leather generally fails the flex test used in this application at 200 (0.2 X 10") flexes and shows no surface resistance to water or oil. A measurable improvement in properties is shown when the combined weight of chromium complex and carbodiimidecompound together amounts to as little as 0.5 percent by weight of the dry leather. For severe use,

such as in suede shoes, about 3 percent by weight of the dried leather is required; more than 6 percent by weight does not appear to offer additional value for most applications. The most useful range of application is therefore from about 0.5 to about 6 percent by weight of dry leather.

Any water soluble chromium Werner coordination complex of substituted or unsubstituted alkanoic, i.e., monocarboxylic. acids or fluorinated alkanoic acid which is capable of rendering leather resistant to water (i.e., static water resistant) may be used in this invention.

Unsubstituted alkanoic acids may contain from about eight to carbon atoms per molecule. Substituted alkanoic acids may include acids from methanoic to tetradecanoic acid having aromatic or fluorinated substituents occupying any position.

Aromatic substituents are generically of the form C,,H where n is at least 6, m is l-3 inclusive and (2n6m-l) is a positive integer and include phenyl,

lower alkyl substituted phenyl. naphthyl and the like such that the aromatic substituted alkanoic acid includes a total of seven to 20 carbon atoms and preferably includes an alkylene chain of at least one carbon atom.

Fluorinated substituents are fluoroaliphatic radicals of three to l 8 carbon atoms with terminal CF as more fully described above, either directly attached to a carboxyl group or indirectly attached to a carboxyl group through an alkylene chain or through a linking group, such as carbonamido or sulfonamido and an alkylene chain in proportions such that the fluoroaliphatic substituted alkanoic acid contains from 10 to 72% carbonbonded fluorine. For convenience, these alkanoic acids with fluorinated substituents are herein termed fluoroaliphatic carboxylic acids, i.e., carboxylic acids containing fluoroaliphatic radicals.

Exemplary carboxylic acid for the formation of chromium complexes suitable for use in the invention include:

The water soluble chromium complexes (prior to hydrolysis) must be soluble in water at 120 F. (49 C.) to an extent of at least 0.1% by weight. A simple test for evaluating the ability ofa chromium complex to impart water repellency or resistance to water may be conducted as follows: A 20 gram sample of chrometanned, retanned, colored and desirably fat-liquored suede leather and about grams of water are placed in a glass container, and the pH is adjusted to 3-4 with formic acid. An amount of the chromium complex equal to 5% of the dry leather weight is added, usually as a 20 to 40 weight percent solution in isopropyl alcohol and the mixture is tumbled for 45 minutes at F. (49 C The leather sample is removed and squeezed to remove excess liquid. After drying completely in a circulating air oven at F. (66 C.), the sample is tested for water repellency by the procedures of ASTM D 1913-61T. A spray rating of at least 50 is considered to indicate water repellency or static water resistance.

Suitable fluorine-free chromium complexes and their preparation are described in U.S. Pat. Nos. 2,273,040; 2,356,161 (showing chromium complexes of aralkyl carboxylic acids, such as those having a phenyl ring nucleus as a substituent on the alkyl group); 2,524,803 and 2,683,156. Fluorochemical chromium complexes and their preparation are described in French Pat. No. 1,396,008, e.g., chromium complex of CF;,CF(CF Cl)C F CONHCl-l COO1-l, and U.S. Pat. Nos. 2,662,835 (showing fluorinated alkyl carboxylic acids in which the alkyl radical can be straight or branched chain alkyl or cycloalkyl); 2,934,450, 3,088,958 and 3,651,108 (showing chromium complexes of perfluoroether carboxylic acids). Other useful fluorinated carboxylic acids which may be used to prepare chromium complexes are described in U.S. Pat. No. 3,232,970, perfluoro 3 amino carboxylic acids in U.S. Pat. No. 3,471,484 and unsaturated fluoroaliphatic carboxylic acids in U.S. Pat. No. 3,646,117. It will be recognized that the various techniques for producing Werner type chromium complexes permit selection of a wide variety of compounds from which the many useful chromium complexes can be prepared.

Carbodiimides are conveniently obtained by condensation of isocyanates in the presence of suitable catalysts as described, for example, in the patents of Table l and by Campbell et al., J. Org. Chem., Vol. 28, Pages 2069-2075 (1963).

Table 1 Inventor US. Patent No. Title Balon 2.853.518 Chemical Process Campbell and 2.853.473 Production of Verbanc Carbodiimides Campbell 2.941.966 Carbodiimide Polymers Smeltz 2.941 .983 Urethane-Terminated Polycarbodiimides Hoeschelc 3,450,562 Cellulosic Materials Coated with an Organic Polycarbodiimide British 1.224.635 Stabilized Polyester Patent Shaped Articles convenience by the general formula:

Bl\'=C=NA),. N=C=1\'B where n is 0 or an integer from 1 to at least 20 and is preferably from O to 10. A and B are organic groups as defined below. The A groups or B groups may each be the same or different. Carbodiimides in which n is 20 and higher are useful but offer no known advantages. A groups are divalent, B groups monovalent and both are free from readily hydrolyzable groups other than isocyanate, isocyanate-reactive active hydrogen atoms and preferably free from non-aromatic unsaturation.

Because the monovalent B groups terminate the carbodiimide molecule at each end, the relative proportion of monoisocyanate to diisocyanate used in the reaction determines the average value of n in the above formula, 0 when no diisocyanate is used upwards so that with about mole percent of monoisocyanate n will average about 20, as will be readily apparent.

In the above general formula, A is a divalent organic group, which may include pendent fluoroaliphatic radical, linking successive carbodiimide groups when n is l to at least 20. Illustrative linking groups include alkylene, such as ethylene, isobutylene, and the like of two to about 10 carbon atoms, aralkylene, such as CH C.,H CH of up to about 10 carbon atoms, po-

lyoxaalkylene such as (C H O) C H containing up to about five oxa groups and combinations of the various types. It will be recognized that the A group is preferably the residue of an organic diisocyanate, that is, the divalent radical obtained by removal of the isocyanate groups from an organic diisocyanate which may include fluoroaliphatic groups. Suitable organic diisocyanates may be simple, e.g., tolylene diisocyanate, or complex, as formed by the reaction of a simple diisocyanate with a dior polyol in proportions to give an isocyanateterminated polyurethane.

Although the carbodiimides generally and preferably include divalent A groups, some of the A groups can be, for example, trivalent or tetravalent, derived from triisocyanates or tetraisocyanates such as polymethylenepolyphenyl isocyanate, e.g., OCNC H CH C H (NCO)CH C H NCO. When A is trivalent or tetravalent, branched or even crosslinked, polycarbodiimides result. A mixture of A groups containing the trivalent groups can be used to provide branched polycarbodiimides which retain the desirable solubility and thermoplasticity of the linear carbodiimides from divalent A groups.

Upper limits of the sizes of A and B groups are such that the carbodiimide groups (N4I=N-) constitute about 10% or more of the molecule except for terminal and pendent fluoroaliphatic radicals present.

Substituents may be present in A groups provided they contain no isocyanate-reactive hydrogen atoms; that is, groups such as -OH are normally excluded. Simple unsubstituted organic linking groups free from nonaromatic unsaturation are preferred. The organic linking group depends on the diisocyanate compound employed such as:

and CH The terminal groups, or B-groups, are monovalent radicals usually of monoisocyanate compounds which may be aliphatic as C H aralkyl as C H CH aryl as C H and preferably fluoroaliphatic such as C F C H and C F, CH O CNHC H ,(CH (derived from tolylene diisocyanate and l,l-dihydroperfluorooctanol). Numerous other terminal groups are operable in the 'process of the invention. The B group can be derived from a diisocyanate by a reaction which is terminated before all NCO groups are consumed and results in B groups containing NCO radicals, e.g. OCNC H -,(CH from tolylene diisocyanate or OCNCH C H CH from xylylene diisocyanate.

A particularly preferred class of carbodiimides is that in which the B moiety is derived from a fluoroaliphatic radical-containing alcohol by reaction with one mole of fluorine-free diisocyanate such as toluene diisocyanate, hexamethylene diisocyanate, or xylylene diisocyanate (-OCNCH C H CH NCO).

While the type of carbodiimide is shown as the reaction product of diisocyanates, branched carbodiimides are perfectly satisfactory. Such materials are derived, for example, from the reaction of monofunctional alcohols or monofunctional fluoroaliphatic radical-containing isocyanates with'trior tetraisocyanates. preferably in combination with diisocyanates.

The B moieties may be the same or different and may comprise mixtures of fluorinated and fluorine-free terminal radicals. The molecular weight of the carbodiimide is relatively unimportant. It should, however. be sufficiently high to provide a material which melts above about 35 C. and below about 200 C. Lower melting materials tend to give an undesirable greasy character to the leather surface and materials melting above 200 C. provide a leather which is less retentive of properties after abrasion.

While the 8" groups have been discussed as derived from isocyanates by reaction with alcohols. they can in general be derived by reaction with any suitable fluoroaliphatic or hydrocarbon compound having an active-hydrogen containing terminal group such as a hydroxyl group (-OH), a carboxyl group (-COOH), mercapto group (-SH) or amino group (-NHR), in which R is hydrogen or lower alkyl of 15 carbon atoms. The following compounds both fluoroaliphatic and fluorine-free hydrocarbon are representative only of those which may be incorporated in B" groups.

Fluoroaliphatic compounds Hydrocarbon Compounds CH (CH- ),,,CH. ,OH CH,,CHOHCH=, (CH CH- CH CH hNH CHulCH- COOH CH,1(CH2).,CH. .OH CH3CH2OH CHRCHQCHECHL-CHQOH cu ou CH 1(CH2);SH Each of the above compounds can be reacted in suitable proportions with a polyisocyanate to produce a monoisocyanate.

Preferably, fluoroaliphatic radicals contain a terminal C F group and contribute from 5 to 50 percent by weight of carbon-bonded fluorine to the carbodiimide or to the metal complex in which they occur and at least 0.25% of carbon bonded fluorine in the solids as deposited on leather in the process of the invention.

In treating the collagen type fiber matrix with the aforementioned carbodiimide and chromium complex, anionically charged tanned material (after coloring and fat liquoring) which has been water-rinsed and is still wet, preferably with approximately an amount of water equal to the weight of dry leather, is conveniently used.

The wet processing of leather in a tannery or leather finishing house is normally conducted in a tanning drum. A conventional wood tanning drum is approximately 4.5 meters in diameter and 2.4 meters in length and contains baffles to tumble the contents while the drum is rota-ted. During drum rotation, the mechanical tumbling of the hides tends to produce an increase in temperature, and it is common practice to heat the drum charge to the desired temperature and thereafter permit the tumbling to proceed without temperature control. The drum is initially charged with from 230 to 460 kg. of chrome tanned, shaved and split leather stock. Water is added in an amount from about onehalf the weight of leather stock (short float") to a weight about equal to that of the leather stock (full float). Retanning chemicals, such as quebracho extract or neutral formaldehyde based resin synthetic tanning agents or dialdehyde tanning agents may then be added. After tumbling for a period of time, the spent float liquor is removed and the stock is rinsed. This leaves the leather anionically charged. Usually the stock is dyed, preferably with an acid or direct dye system, and rinsed. The dyed stock is treated with a fat liquor containing e.g., materials of the sulfonated sperm oil type or sulfonated neatsfoot type and is then thoroughly rinsed. Water is added in an amount equal to one-half the leather stock weight and the stock is tumbled at l l0 F. (45 C.) for about 5 minutes. The pH of the float liquor is then checked and adjusted to pH 3.03.5, if necessary, e.g., with concentrated formic acid, and tumbling is continued until the pH remains constant within this range. The desired amount of chromium complex, typically as a 20 to 40 percent by weight solution in water isopropanol, is then added to the drum and the stock further tumbled for 30 to 60 minutes, usually at a temperature in the region of 45 C. until the foam disappears. The desired amount of carbodiimide, generally in the form of a 20 to 40 percent aqueous emulsion, is added to the drum containing the stock, the stock being tumbled for an additional 30 to 60 minutes at about the same temperature. If necessary, a test for exhaustion of the carbodiimide may be conducted by moistening a piece of filter paper with a sample of the float liquor, drying, and placing a drop of water on the dried paper. If the float liquor is properly exhausted, the water will immediately soak into the paper. After draining the float liquor, the leather stock is removed for finishing in the normal manner. Alternatively, the chrome complex and carbodiimide may be combined as a solution or aqueous suspension and the stock treated with both simultaneously. The sequential treatment with aqueous liquors is generally more effective and is preferred.

The invention is now further illustrated by a number of examples. Some of the examples, as will be indicated, are for comparison with prior art and some illustrate the process of the invention and leather treated by the process. In these examples, leather samples are L2 to 1.6 mm. thick brushed pigskin in speciments mm. X 200 mm. The leather is chrome-tanned, retanned with a neutral synthetic tanning agent (such as sulfonated naphthalene-formaldehyde condensate) colored with acid dye (grey-green) and fat-liquored. The samples are treated at 50 C. from a short aqueous float in which the pH is adjusted to 3.0 to 3.5 with formic acid prior to addition of carbodiimide and chromium complex.

After treatment, samples are rated for dynamic water resistance, static oil and water resistance and surface oil repellency. Insofar as possible all treatments are applied to leather samples having as nearly identical properties as possible, but it will be recognized by those having skill in leather technology that leather samples may vary widely in properties even when taken from the same hide. Accordingly, although the numerical results fairly represent relative ratings of the samples tested, repetition of these tests at other times may mot duplicate numerical results but should place analogous samples in the same relative positions. This is the nature of working on materials subject to much natural variation. Likewise, repetition of the tests in other sueded leathers, e.g., calf, kid, steer, horse, Chamois, etc., will give substantially the same relative positions.

Static oil and water resistance are measured by an absorption test using 50 mm. X 50 mm. squares cut from a treated sample. Squares are weighed, weighted and hung in the respective liquids. For oil resistance, the sample is suspended in mineral oil for minutes so that the upper edge is 6 mm. below the surface of the oil. For water resistance, the sample is suspended in water for 1 hour with the upper edge mm: below the surface. The squares are then removed, blotted lightly, reweighed, and the increase in weight expressed as a percent of the original weight. No allowance is made for soluble components in the leather which may be extracted.

Dynamic water resistance is measured in a Maeser Flex Tester on 115 mm. X 115 mm. samples in accor- VII.

dance with ASTM method D-2099-70.

Surface oil repellency is measured in accordance with Test 1 18-1966T of American Association of Textile Chemists and Colorists on 120 mm. X 150 mm. samples before and after abrasion. In this test higher numbers indicate superior oil resistance. The abrasion is carried out by brushing the sample back and forth with moderately tine (80 grit) sand paperin one direction, rotating the sample 90 and brushing back and forth again until the surface is entirely covered, then brushing five times back and forth in each direction with a brass bristle brush.

In all the following examples, a fluoroaliphatie group containing chromium complex is used with certain exceptions.(Runs 3, 4 use none; 2 is a control with hydrocarbon complex and 7 and 19 are run with hydrocarbon complex). The fluorine containing complex (FCC) used here as exemplary is N-ethylperfluorooctanesul- Eight carbodiimides (designated 11 through 1X) are used to demonstrate the invention. All contain fluoroaliphatic groups except for VIII. The severa structures and individual designations are:

EXAMPLE l This example serves to provide comparisons at various levels of application between the compositions used in the invention including Carbodiimides 11 and analogous compositions using Urethane 1. Samples are prepared and tested as described above. Except as indicated by footnotes or annotations, the total of carbodiimide or urethane (column headed adduct") plus" chromium complex (FCC except where noted as l-lC C) is 2% by weight of dry leather. Slashes are used to separate data pertaining to Carbodiimide 11 from those on Urethane l, i.e., Run 3 is for '11; Run 4 for 1.

Table l 71F Static Surface oil repellency Static Dynamic Water I 7( on oil Before After water Resistance Run adduct I leather uptake 71 Abrasion Abrasion uptake 7: (Maeser Flex X 10") 3/4 2 0.86/0.72 15/11 4/4+ 5/3+ 41/45 13/7 14/4a 0.33" 0.20/0.18 12/11 2+/2+ 3+l3+ 48/48 1/0.5 15/5 0.7" 040/035 13/18 3/2+ 4+/1+ 44/59 8/0.5 16/11 0.3 0.69/0.67 22/35 5/4 1/0 43/51 8/3 17/ 10 0.7 0.73/0.68 12/15 3+/2+ 2+/1+ 44/56 12/9 18/9 1.0 0.76/069 10/17 4/3 3+/2+ 36/53 14/6 79/7 l.3** 0.56/0.47 10/14 3+/2+ 4+ll+ 48/58 ll/2 20/6 1.3 0.79/0.70 15/20 5/4 5/2+ 42/36 16/2 21/8 1.7 0.83/0.710.71 11/11 5/5 4+l3+ 47/58 18/10 22/12 2.7 0.16/040 10/15 4/3+ 5/2 28/40 27/5 Table l-continued %F Static Surface oil repellency Static Dynamic Water on oil Before After water Resistance Run adduct leather uptake 92 Abrasion Abrasion uptake '12 (Maeser Flex X 10") 23/l3 4.0" 0.38/0.l 9/l2 4/4+ 5/4 34/40 42+/l3 Controls. no adduct. l with FCC. 2 with HCC with HCC "-Tutal 0.50 "-Tutal L00 "-Tutal 4.0% "-Total 6.0%

EXAMPLE 2 This example illustrates various compositions of the l 5 invention using Carbodiimides ll through lX. All are employed at a level of 2% by weight of dry leather of which two thirds (l.7%) is the carbodiimide and the balance of (0.7%) is the fluoroaliphatic chrome complex designated FCC.

ll. fluoroaliphatic carboxylic acid having at least one terminal CF group and containing from to 72% of carbon-bonded fluorine in fluoroaliphatic groups.

B. an aqueous float liquor containing carbodiimide containing about 10% or more by weight of N=C=N groups in the weight of the molecule excluding terminal or pendent fluoroaliphatic radi- Static Surface oil repellency Static Dynamic Water F oil before after water Resistance Run Carbodiimide on leather uptake (i abrasion abrasion uptake 11' (Maeser Flex IO) 4 ll 0.79 l5 5 5 4] I6 15 Ill 0.70 l5 4 3+ 4i 6 6 l\' 0.62 21 4 0+ 32 36 27 0.80 12 5 5 I9 4 28 VI 0.7l 18 4+ 3+ 3'. Z4 29 V" 0.63 l4 4+ l 31 14 30 VI" 023 49 2 0 48 9 3 l IX 0.55 l l 4+ 3 31 I3 It will be evident that Carbodiimide Vll (which contains no fluoroaliphatic radicals provides improved dynamic water resistance but only limited surface oil repellency and for this reason, fluoroaliphatic carbodiimides are usually preferred.

What is claimed is:

1. Process for improving the dynamic water resistance of porous anionically charged collagen fiber matrix comprising treating said matrix, while water wetted. consecutively or concurrently with:

A. an aqueous float liquor containing a water soluble chromium complex of substituted or unsubstituted alkanoic acid B. an aqueous float liquor containing carbodiimide having a content of 'N=C=N groups of about l0% or more by weight in the weight of the molecule excluding terminal or pendent fluoroaliphatic radicals.

2. Process for improving the dynamic water resistance of porous anionically charged collagen fiber matrix comprising treating said matrix, while water wetted. consecutively or concurrently with:

A. an aqueous float liquor containing a water soluble chromium complex of l. aliphatic carboxylic acid of eight to 20 carbon atoms unsubstituted other than by aromatic groups C,,H where n is at least 6 and m is an integer from I to 3 inclusive and (2n6m-l) is a positive integer.

cals, said carbodiimide being represented as:

BN=C=N- A,, N=C=NB where n is 0 to 20 and A and B are respectively divalent and monovalent organic radicals free from readily hydrolyzable groups other than isocyanate and are free from isocyanate-reactive active hydrogen atoms; the weight ratio of said chromium complex and said carbodiimide being from 1:9 to 9:1 and the combined weight of said chromium complex and carbodiimide in said float liquors being from 0.5 to 6.0% based on the dry weight of said collagen fiber matrix.

3. Process according to claim 2 wherein the carbodiimide contains fluoroaliphatic radicals giving from 5 to by weight of carbon-bonded fluorine.

4. Process according to claim 2 wherein the carbodiimide is free from non-aromatic unsaturation in the organic radicals.

5. Process according to claim 2 wherein the anionically charged collagen fiber matrix is retanned and dyed leather.

6. A collagen fiber matrix comprising, in insolubilized form, from about 0.5 to 6.0% by weight on a dry basis of the combination of a water soluble chromium complex and carbodiimide in proportion of 9:1 to 1:9.

7. Collagen fiber matrix according to claim 6 wherein the insolubilized combination of chromium complex and carbodiimide provides 0.25 percent or more carbon-bonded fluorine based on the weight of the collagen fiber matrix.

8. Collagen fiber matrix according to claim 6 wherein sueded leather constitutes the matrix.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT N0. 922,118 DATED 1 November 25, 1975 INVENTO I John M. Schuster and Maynard H. Olson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as strewn below:

Column 4, line 68, "BN=C=N-A) N=C=NB" should Column 8, line 59, "mot" should read not I n Column 10, lines 8 9 (0 F S0 N(C H )C H O CNHC H CH C H NHCO C H should read (C F SO N(C H )C H O CNHC H CH C H NHCO C H N II II f Column 10, Formula V, C F StI should read C F oO Under oolumn headed "Run" in Table I, should read 1* e Bigncd and Scaled this Nineteenth Day of October 1976 [SEAL] AIICSI.

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner ofParents and Trademarks 

1. PROCESS FOR IMPROVING THE DYNAMIC WATER RESISTANCE OF POROUS ANIONICALLY CHARGED COLLAGEN FIBER MATRIX COMPRISING TREATING SAID MATRIX, WHILE WATER WETTED, CONSECUTIVELY OR CONCURRENTLY WITH: A. AN AQUEOUS FLOAT LIQUOR CONTAINING A WATER SOLUBLE CHROMIUM COMPLEX OF SUBSTITUTED OR UNSUBSTITUTED ALKANOIC ACID AND B. AN AQUEOUS FLOAT LIQUOR CONTAINING CARBODIIMIDE HAVING A CONTENT OF -N=C=N-GROUPS OF ABOUT 10% OR MORE BY WEIGHT INTE WEIGHT OF THE MOLECULE EXCLUDING TERMINAL OR PENDENT FLUOROALIPHATIC RADICALS.
 2. Process for improving the dynamic water resistance of porous anionically charged collagen fiber matrix comprising treating said matrix, while water wetted, consecutively or concurrently with: A. an aqueous float liquor containing a water soluble chromium complex of I. aliphatic carboxylic acid of eight to 20 carbon atoms unsubstituted other than by aromatic groups CnH n m where n is at least 6 and m is an integer from 1 to 3 inclusive and (2n-6m-1) is a positive integer. II. fluoroaliphatic carboxylic acid having at least one terminal CF3 group and containing from 10 to 72% of carbon-bonded fluorine in fluoroaliphatic groups. B. an aqueous float liquor containing carbodiimide containing about 10% or more by weight of -N C N- groups in the weight of the molecule excluding terminal or pendent fluoroaliphatic radicals, said carbodiimide being represented as: B-N C N- An N C N-B where n is 0 to 20 and A and B are respectively divalent and monovalent organic radicals free from readily hydrolyzable groups other than isocyanate and are free from isocyanate-reactive active hydrogen atoms; the weight ratio oF said chromium complex and said carbodiimide being from 1:9 to 9:1 and the combined weight of said chromium complex and carbodiimide in said float liquors being from 0.5 to 6.0% based on the dry weight of said collagen fiber matrix.
 3. Process according to claim 2 wherein the carbodiimide contains fluoroaliphatic radicals giving from 5 to 50% by weight of carbon-bonded fluorine.
 4. Process according to claim 2 wherein the carbodiimide is free from non-aromatic unsaturation in the organic radicals.
 5. Process according to claim 2 wherein the anionically charged collagen fiber matrix is retanned and dyed leather.
 6. A collagen fiber matrix comprising, in insolubilized form, from about 0.5 to 6.0% by weight on a dry basis of the combination of a water soluble chromium complex and carbodiimide in proportion of 9:1 to 1:9.
 7. Collagen fiber matrix according to claim 6 wherein the insolubilized combination of chromium complex and carbodiimide provides 0.25 percent or more carbon-bonded fluorine based on the weight of the collagen fiber matrix.
 8. Collagen fiber matrix according to claim 6 wherein sueded leather constitutes the matrix. 